The SCSI adapter devices and the SCSI controller devices for peripherals are simple and cost effective, highly standardized, and often built into the computers and peripherals designed for the bus. Each device on the bus has a priority, and the highest priority device for communication control has to win the rights for the use of the bus. The negotiation for the control of the bus is conducted within a predetermined time window to all devices, but each SCSI device on the bus acts independently for the detection of the time-window.
Serial Attached SCSI (SAS) is the next generation of the Small Computer System Interface (SCSI), used for connecting storage devices to a computer system. It has been developed as an alternative to the Fiber Channel interface (FC), offering similar performance and reduced cost, at the expense of connectivity and scalability. Because it is an electrical technology as opposed to optical, it has a distance limitation of 10 meters, making it useful only inside cabinets and for peripherals that are physically located next to the computer system that uses the interface. It would be useful to have a means of using the SAS technology without having to sacrifice the ability to have remote connectivity for storage. Unfortunately, the timings for SAS are such that the propagation delay associated with long distance links over one hundred meters will become problematic without a method to keep the SAS timers from popping. Hence it would be advantageous to have such a method.